$\color{blue}{\fbox{Toán 10}\bigstar\text{Lượng Giác}}$

X

xuanquynh97

1.
PT \Leftrightarrow $sin(3.2x)+1=2cos^4x-1$

\Leftrightarrow $3sin2x-4sin^32x+1=cos^22x$

\Leftrightarrow $3sin2x-4sin^32x+1-(1-sin^22x)=0$

\Leftrightarrow $\left[ \begin{array}{ll} sin2x=1 &\\
sin2x=\dfrac{-3}{4} &\\
sin2x=0 &
\end{array} \right.$
 
Last edited by a moderator:
X

xuanquynh97

2.
PT \Leftrightarrow $9(1-cos^2x)-10(1-cos^2x)cosx+17cosx-11=0$

\Leftrightarrow $9-9cos^2x-10cosx+10cos^3x+17cosx-11=0$

\Leftrightarrow $cosx=\dfrac{2}{5}$
 
You must log in or register to reply here.
Top Bottom